Lithium polyorgano siloxane polymer grease compositions



Patented July 27, 1954 LITHIUM IPOLYORGANO SILOXANE POLY- MER GREASE COMPOSITIONS Stephen J. Zajac, Whiting, Ind., assignor to Standard ()il Company, Chicago, 111., a corporation of Indiana No Drawing. Application June 2, 1952, Serial No. 291,323

This invention relates to high temperature greases and more particularly pertains to lithium soap silicone polymer greases having high temperature stability characteristics and to the method of preparing such greases.

The preparation of stable lithium soap silicone greases by conventional methods is very diflleult requiring the use of milling operations and/or the use of solvents which must be removed. In addition, such greases require a relatively high soap content.

It is an object of the present invention to provide a lithium soap silicone polymer grease which is stable at high temperatures with respect to consistency and which is resistant to leakage at high temperatures. Another object of the invention is to provide a lithium soap silicone polymer grease having a high dropping point. Still another object of the invention is to provide a lithium soap silicone polymer grease which will effectively lubricate bearings operating at high temperatures and which will not melt and/or lose consistency at such operating temperatures. A further object of the invention is to provide a method of preparing lithium soap silicone poly mer greases Without the use of volatile solvents. Other objects and advantages of the invention will become apparent from the following description thereof.

I have discovered that the foregoing objects, as Well as others, can be attained with a lubrication grease comprising a major proportion of a silicone polymer oil, 1% to about 20%, and preferably from about 2% to about of a lithium soap of a high molecular weight fatty acid, and a free basic compound in amounts of from about 10% to about 500%, and preferably from about 50% to about 300% based on the lithium soap content of the grease. The lithium soap employed in the grease composition of the present invention is a soap or an unsaturated, partially unsaturated or saturated fatty acid or a hydroxy fatty acid having at least 12 carbon atoms, and preferably from about 12 to 22 or more carbon atoms. Examples of suitable fatty acids are lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, StandardF-atty Acids, hydrogenated fish oil fatty acids, hydrogenated castor oil, hydroxy stearic acid, e. g., 1 hydroxy stearic acid, and the like. The term high molecular Weight fatty acid, as used herein and in the appended claims, means a fatty acid having at least 12 carbon atoms. Standard Fatty Acids is a product well known in the grease making trade, and comprises about 40% animal fatty acids and about 60% cottonseed fatty acids.

The specific eifectiveness of the various fatty acids varies to some extent, the lithium soaps of 18 Claims. (Cl. 252-42.1)

all or them, however, being effective to various de grees. It is, therefore, not to be implied that the lithium soaps of all of the herein-described fatty acids are equivalents.

The required excess alkalinity of the grease can be supplied by incorporatin in the grease composition from about 10% to about 500%, or more, and preferably from about 50% to about 300% based on the soap content of the grease, of a basic compound such as basic alkali metal compounds, basic alkaline earth compounds, and high boiling basic organic nitrogen compounds, such as allphatic or aromatic amines boiling above about 250 F.

Examples of suitable basic compounds are sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium oxide, barium hydroxide, barium oxide, calcium hydroxide, calcium oxide, triphenyl amine, octylamine, etc.

The silicone oil polymers employed as the grease vehicle is suitably a polymeric liquid compound having the general formula in which R, R1, R2, R3, R4, and R5 are the same or diiferent hydrocarbon radicals, such as alkyl, aryl, alkaryl or aralkyl radicals and n is an integer greater than 1. Depending upon the extent of condensation or polymerization, the polymer products vary from relatively light liquids to solid resins. However, for the purpose of the present invention, polymers which are high boiling liquids within the lubricating oil viscosity range are preferred. Commercially available compounds of this type are polymers of dimethyl silicone, diethyl silicone, ethylmethyl silicone, diphenyl silicone, ditolyl silicone, methyl phenyl silicone, ethyl phenyl silicone, and the like. Other silicone polymers produced from high molecular. weight hydrocarbon groups, such as butyl, amyl, hexyl and above, when economically available can also be used. Polymeric organic siiicon compounds of this type are also referred to as polymeric dihydrocarbon siloxanes or polyorgano siloxanes.

Greases of the present invention are easily prepared and do not require the use of solvents which must be subsequently removed as is made necessary by prior art methods of preparing such greases. In preparing greases of the present invention, all of the lithium soap, a portion of the polyorgano siloxane and all of the basic com pound, preferably in the form of an aqueous solution or suspension, of about 5% to about 35%, are mixed together, slowly heated to a temperature of about 212 F., and maintained at this temperature until the mixture is substantially free of 3 water. When the mixture is substantially anhydrous, and foaming, if any, subsides, the remaining portion of the polyorgano siloxane is added, the batch heated to a temperature of from about 450 F. to about 550 F., and preferably to a temperature of about 500 F. to 510 F., and maintained at said temperature until the reaction is completed. lhe grease is then filled and cooled. The cooled product, if desired, can be homogenized by well known means.

A. preferred grease stable at temperatures of at least about 450 F. is illustrated by the following composition:

Per cent Lithium hydroxy stearate 1-10 Alkali metal or alkaline earth hydroxide 2-10 Polyorgano silicone 80-97 Grease compositions made in accordance with the hereindescribed invention are illustrated. by the following examples in Table I:

1 National Lubricating Grease Institute Grades. 2 Dow Corning Silicone Oil N o. 550-SSU300400 at 100 F.

In each of the above examples, there was no change in the appearance or structure of the grease during the dropping point test made in accordance with the A. S. T. M. method 13-566-42. Examples I to IV are transparent, smooth and buttery and light-colored greases. The greases of Examples V and VI are opaque, light-colored, and while mealy in structure, can be molded for high temperature plug valve lubricants and for greases.

The present invention is not only applicable to greases containing lithium hydroxy stearate but is also applicable to greases compounded with lithium soaps of other fatty materials. The following examples in Table II illustrate the application of the present invention to silicone polymer greases containing lithium soaps of various fatty materials.

Table II Example No I-A N. L. G. I. Grade Lithium soap of Hydrogenated castor oil Olcic acid Standard Fatty Acid 12-hydroxy stearic acid-.. Lithium monohydrate Silicone Polymer oil Micro-penetration, un-

worked Micro-penetration. work- +550. Mahogany White.

Approximately 40% animal fatty acid: 60% cottonseed fatty acid.

3 Dow Corning Silicone Oil No. 550.

Although in the foregoing examples excess alkalinity of the grease was imparted by the use 4 of lithium hydroxide monohydrate, other alkaline materials can be efiectively employed for this purpose. Greases prepared with alkaline agents other than lithium hydroxide, are illustrated by the examples of Table 111:

Table III Example No. I-B II-B IIIB IV-B V-B Lithium l2-hydroxy stcarate percent" 5.0 2.0 2.0 4.0 2.0

Alkaline agent:

Sodium hydroxide d0 5.0

Potassium hydroxide. do. 2.0

Barium hydroxide "do" Hydrated lime do Triphenyl amine do Silicone polymer oil 1 ..do 90. 0 v 0 90. 0 92.0 92.0 Micro-penetration, un\vorked 60 41 289 170 451 Micro penetration, worked" 56 Dropping Point, "F +420 +429 293 282 Table IV Example No. I-O

N. L. G. l. Grade 2 Lithium l2-hydroxy stearate. Lithium hydroxide monoliydra Silicone Polymer Oil 1 Silicone Polymer Oil 2 Mi ro-penetration. unworlred Microbenetration, worked Dropping Point, "F Color 1 Dow Corning S lidonc Oil No. 200 ssU at F.355. 2 Dow Corninu Silicone Oil N0. 710 SSU at 100F.1060.

The micro-penetration data given in the foregoing tables were determined by the proposed method described on page 339 of the November 194.0 issue of A. S. T. M. Standard on Petroleum Products and Lubricants.

Grease compositions prepared by the method ascribed herein exhibit essentially the same consistency at room temperatures as at temperatures as high as 500 This property makes such greases especially suitable for use in the lubrication of moving parts operating at temperatures ranging from room temperatures to temperatures excess or" about 300 E.

A high temperature hearing test, conducted. at 10,000 R. P. lvl. and at 450 IT, was made on a 3 gram sample of a grease comprising 1% lithium l2-hydroxy stearate, 2% lithium hydroxide rnonohydrate and 97% Dow Corning Silicone Oil No. 550. At the end of hours the seeing was still in good condition.

In the foregoing examples the silicone polymers designated Dow Corning Silicone Oil No. 550 and No. 210 were inethylphenylpolysiloxanes, the latter having a higher phenyl/methyl ratio. The silicone polymer designated Dow Corning Silicone Oil No. 2-30 was a methylpolysiloxane.

Percentages given herein and in the appended claims are weight percentages unless otherwise specified. i

While I have described my invention by reference to specific preferred embodiments thereof, it is not intended that the invention be limited thereby but includes within its scope such modifications and variations as come within the spirit of the appended claims.

I claim:

1. A lubricant grease composition comprising a major proportion of a liquid polyorgano siloxane, from about 1% to about 20% of a lithium soap of a fatty acid, and a free basic compound lithium soap content of said composition, said polyorgano siloxane having the general formula in which R, R1, R2, R3, R4 and R5 are hydrocarbon radicals.

2. A lubricant grease composition described in claim 1, in which the lithium soap is lithium stearate.

3. A lubricant grease composition as described in claim 1, in which the lithium soap is lithium 12-hydroxy stearate.

4. A lubricant composition described in claim 1, in which the lithium soap is a soap of hydrogenated castor oil.

5. A lubricant grease composition described in claim 1, in which the lithium soap is lithium oleate.

6. A lubricant composition described in claim 1, in which the basic compound is a basic alkali metal compound.

'7. A lubricant composition described in claim 1, in which the basic compound is lithium hydroxide monohydrate.

8. A lubricant composition described in claim 1, in which the basic compound is sodium hydroxide.

9. A lubricant composition as described in claim 1, in which the basic compound is a basic alkaline earth compound.

10. A lubricant grease composition described in claim 1, in which the basic compound is barium hydroxide.

11. A lubricant grease composition described in claim 1, in which the basic compound is hydrated lime.

12. A lubricant grease composition described in claim 1, in which the basic compound is a basic organic amine.

13. A lubricant grease composition described in claim 1, in which the polyorgano siloxane is a methylpolysiloxane.

14. A lubricant grease composition described in claim 1, in which the polyorgano siloxane is a methylphenyl polysiloxane.

15. A lubricant grease composition comprising a major proportion of a liquid polyorgano siloxane, from about 1% to about 20% of a lithium soap of a high molecular weight hydroxy fatty acid, and lithium hydroxide in an amount equivalent to at least of the lithium soap content of said grease composition, said polyorgano siloxane having the general formula R1 R3 R -si-o)..si-R5 1. t.

in which R, R1, R2, R3, R4 and R5 are hydrocarbon radicals selected from the class consisting of methyl radicals, phenyl radicals and mixtures thereof.

16. A lubricant grease composition comprising a major proportion of a liquid polyorgano siloxane polymer, from about 1% to about 10% of a lithium l2-hydroxystearate and from about 2% to about 10% of an alkali metal hydroxide, said polyorgano siloxane having the general formula in which R, R1, R2, R3, R4 and R5 are hydrocarbon radicals selected from the class consisting of methyl radicals, phenyl radicals and mixtures thereof.

17. A lubricant grease composition comprising from about to about 97% of a liquid polyorgano siloxane polymer, from about 1% to about 10% lithium hydroxystearate and from about 2% to about 10% of an alkaline earth hydroxide, said polyorgano siloxane having the general formula in which R, R1, R2, R3, R4 and R5 are hydrocarbon radicals selected from the class consisting of methyl radicals, phenyl radicals and mixtures thereof.

18. A method of preparing a lubricant grease composition comprising a major proportion of a liquid polyorgano siloxane having the general formula in which R, R1, R2, R3, R4 and R5 are hydrocarbon radicals, from about 1% to about 20% of a lithium soap of a fatty acid, and a free basic compound in an amount equivalent to about 10% of the lithium soap, which method comprises mixing together all of the lithium soap, a portion of said polyorgano siloxane, and all of the basic compound in aqueous solution, heating said mixture to a temperature of about 212 F., maintaining the mixture at said temperature until the mixture is substantially anhydrous, adding the remaining portion of said polyorgano siloxane to said mixture, heating the mixture to a temperature of from about 450 F. to about 550 F., maintaining said mixture at said temperature until the reaction is complete, and filling and cooling said finished grease product.

References @ited in the file of this patent UNITED STATES PATENTS Number Name Date 2,446,177 Hain Aug. 3, 1948 2,450,221 Ashburn et a1 Sept. 28, 1948 2,450,222 Ashburn et a1 Sept. 28, 1948 2,455,642 Marker Dec. 21, 1948 2,508,741 Ashburn et a1 May 23, 1950 2,599,984 Fletcher et a1 June 10, 1952 2,606,153 Holdstock Aug. 5, 1952 2,616,850 Browning Nov. 4, 1952 2,636,001 Browning Apr. 21, 1953 

1. A LUBRICANT GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF A LIQUID POLYORGANO SILOXANE, FROM ABOUT 1% TO ABOUT 20% OF A LITHIUM SOAP OF A FATTY ACID, AND A FREE BASIC COMPOUND LITHIUM SOAP CONTENT OF SAID COMPOSITION, SAID POLYORGANO SILOXANE HAVING THE GENERAL FORMULA 